In recent weeks, people unhappy with Mastodon project talked about forking the project in a different direction. It's harder than it looks.
A lot of people have talked about the possibility of forking Mastodon to get the many improvements their communities need. Making such an effort successful is another discussion entirely.
It absolutely is. Yet, as Sean said, it’s also yet another bit of software to run and maintain, and ES is known to be a bit of an effort to keep going well.
Admins having only finite amounts of time and/or resources, might make the very understandable decision to leave it out.
It is about as common as using a database server for content though to use something like ES, Solr or similar software for search.
It absolutely is. Yet, as Sean said, it’s also yet another bit of software to run and maintain, and ES is known to be a bit of an effort to keep going well.
Admins having only finite amounts of time and/or resources, might make the very understandable decision to leave it out.